In general; the invention relates to controlled vehicle suspension systems. More specifically, the invention relates to coefficients of force being offset through suspension damping, and in particular, to a method and system for providing independent axle controls for use with suspension damping control outputs.
Known variable force suspension systems include variable force shock absorbers and/or struts that provide suspension-damping forces at a magnitude controllable in response to commands provided by a suspension system controller. Some systems provide control between two damping states and others provide continuously variable control of damping force.
In a known manner of control of a variable force suspension, the demand force for each variable force damper is determined responsive to a set of gains, the wheel vertical velocity and the body heave, roll and pitch velocities. An example system determines the demand force as follows: DFb=GhHxe2x80x2+GrRxe2x80x2+GpPxe2x80x2+Gwv, where DFb is the demand force, Gh is the heave gain, Gr is the roll gain, Gp is the pitch gain, Gw is the wheel velocity gain, Hxe2x80x2 is the body heave velocity, Rxe2x80x2 is the body roll velocity, Pxe2x80x2 is the body pitch velocity and v is the wheel vertical velocity. The portion of the demand force computation GhHxe2x80x2+GrRxe2x80x2+GpPxe2x80x2, represents the body component determined responsive to the body heave, roll, and pitch velocities. The portion of the demand force computation Gwv represents the wheel component determined responsive to the difference between the computed body corner velocity and the body-wheel relative velocity.
A control signal representing the determined demand force is output to control the variable force damper responsive to the demand force. Example variable force damper systems are described in U.S. Pat. Nos. 5,235,529, 5,096,219, 5,071,157, 5,062,657, and 5,062,658.
Modules are typically used by variable force damper systems for identifying and controlling different aspects of automotive control. The modules typically use specialized algorithms designed for interpreting the automobiles input forces for a preferred control signal. One module known in the art commands individual damper outputs to a minimum damping state whenever the applicable desired force and damper wheel to body velocity signals are opposite in sign (a state in which the given damper is said to be in an xe2x80x9cactivexe2x80x9d quadrant). Within the limits of damper travel for small to medium-sized inputs, this approach provides acceptable vehicle body motion control. However, on larger inputs that cause the limits of damper travel to be tested, the absence of damping in the xe2x80x9cactivexe2x80x9d quadrants can allow very undesirable compression and/or rebound bumpstop impacts. In this context, compression and rebound bumpstops are defined as damper positions at which either full metal to metal impact and/or compression of one or more hard rubber parts occurs. To this end, wheel-to-body relative position-based xe2x80x9celectronic bumpstopxe2x80x9d algorithms have been used. Adversely, it has typically been difficult for the existing bumpstop algorithms known in the art to satisfactorily improve compression and/or rebound bumpstop impact energy without undesirable side effects on inputs that do not require the bumpstop algorithms use.
Therefore, it would be desirable to have an algorithm that would improve upon the above-mentioned situation, and related situations in which system control is released prematurely. Such an algorithm may provide superior gross motion control and reduced compression bumpstop activation during large events such as truck swells. Ideally, the algorithm would provide bumpstop and improved body motion control with minimal, if any, sacrifice in ride comfort and impact isolation.
One aspect of the invention provides a method for independent axle control of a variable force damper system by providing at least one axle velocity signal from at least one vehicle sensor. The method then applies an axle control algorithm to the at least one axle velocity signal, thus determining at least one axle damping command as a function of the axle control algorithm.
An additional embodiment of the method for independent axle control of a variable force damper system provides that the axle control algorithm is comprised of an axle velocity determination algorithm, an axle damping command determination algorithm, an axle corner damping command determination algorithm, and an axle damping command slew rate limitation algorithm.
Another embodiment of the invention includes a system for independent axle control of a variable force damper system comprising a means for providing at least one axle velocity signal. Also included is a means for applying an axle control algorithm to the at least one axle velocity signal, and finally, a means for determining at least one axle damping command as a function of the axle control algorithm.
Another embodiment of the invention provides a computer readable medium storing a computer program providing computer readable code for applying an axle control algorithm to an at least one axle velocity signal, and computer readable code for determining at least one axle damping command as a function of the axle control algorithm.
The foregoing and other features and advantages of the invention will become further apparent from the following detailed description of the presently preferred embodiment, read in conjunction with the accompanying drawings. The detailed description and drawings are merely illustrative of the invention rather than limiting, the scope of the invention being defined by the appended claims and equivalents thereof.